When I originally started trying to make Cupric Chloride etchant, I hadn't thought of just using the regular procedure of etching to get there. So I ...

Ferric chloride is a traditional home-use circuit board etchant. It's easy enough to come by, and the Ferric by itself is no big environmental problem. However, once you've etched a board with it, you're left with a solution with a bunch of copper chloride in it. This dissolved copper is an environmental problem, and you can't just pour it down the drain (legally) -- you're supposed to take it to a hazardous waste facility. (For instance: How to Dispose of Ferric Chloride in this FAQ. )

Wouldn't it be nice if there were an etchant that you could re-use indefinitely so that you don't have to worry about disposing of the copper, and that could be made in lifetime supply for like $10.00 with ingredients bought at hardware and drugstores? (And it's prettier too.)

So I made a batch but am curious about my storage container. Its a glass jar with a glass lid an rubber seal that is closed with the clamp. Hopefully you know what I'm talking about. Will this be okay? I just don't want gasses to expand an compromise anything/break the jar.

So .. pool acid and mouthwash.I read in the Ferric Chloride FAQ, that I need Washing soda >> is it enough of the materials you mentioned ?And, how to test it with a paper ? normal paper and what's the sign that the mix is safe to pour?Thank you,

Don't go substituting stuff! (Unless you really know what you're doing.) Hydrogen peroxide _is_ used by some folks as mouthwash, but that doesn't mean any other mouthwash will work.

Hmmm... washing soda. I'm guessing that's to neutralize the acid for disposal? If so, part of the point of this etchant is that you will not need to get rid of any of it for a reasonably long period of time (years? a decade?) because it's renewable. So you shouldn't need that.

And anyway, I'm not sure that knocking down the acid makes it safe to "pour". You'll end up with a different copper compound, but it's the copper that's bad for water sources.

I think when people dispose of stuff this way, they neutralize it first and then let it dry out, and then take it somewhere where you can dispose of hazardous chemicals. But again, we're trying to avoid doing that in the first place.

I live in a place where it's impossible to get acids from a drug store. I can only find acids used in detergents or other cleansing material and so forth. So im wondering if there is any product at a normal market that could be used instead of hydrogen peroxide and hydrochloric acid?

Hydrochloric acid is pretty common. It's used to balance the acidity of pools and to clean concrete. I don't know where you live, but I bet you'll find some.

The peroxide I used was really weak -- the kind that people often use as a mouthwash. But stronger peroxide mixtures are commonly used to bleach hair, for instance.

I'd avoid anything with additional additives. You just don't know what will happen.

(For instance: some people have substituted mostly-NaOH drain cleaners for NaOH, but then it's also got some aluminum flakes in it which make the reaction exothermic, and turn something potentially simple into a safety hazard.)

I've made a mixture of: 1 cup H2O2 36%, 1 cup HCl 23%and made a simple test pcb. I did nothing to start the process first try was slow but second try was much faster. Because there was already some copper in the mixture.I was able to make a trace of 12mill => 0.3mm, my printer was the bottle neck.

Thank you for your project, looks like a good system to me. Do you have a recommendation of what types of plastic I could use as containers for this project? I intend to use it to electroplate graphite painted 3d printed plastics such as PLA/ABS/HIPS/Nylon/TPE, can you think of any issues i might face with any those plastics?

Just one quick question, does the container need to be actively open when using the solution? The reason why I ask is I try to minimize any fumes I can (even when soldering). Like using a small glass pan with modified lid that locks everything air tight as it etches. I don't know if its like a fume pressure build up like smoke would cause, or more extreme like a 6th grade volcano kind of pressure. Thank you.

No problem closing it up as it etches. I always do that so that it doesn't spill while I'm agitating. (I etch in tupperware and slosh it around vigorously.)

Ziplock bags also make a nice etching tank. Board in, fill with etchant, close, and then lay it all flat in some kind of dish or tupperware in case you accidently break or open the bag. You can agitate the board by smooshing the bag (carefully) like a waterbed, and it's really easy to tell when it's done because you can press the bag up against the board like a window.

The other advantage of the tupperware + ziplock bag is that you can easily fill the tupper with warm water which will keep the etchant warm and speed up the reaction.

When you're done, snip off a corner from the bag and you've got a funnel to pour it back into your container.

I think I used too much. All I did was create fumes are irriate my breathing. I'm going to toss the batch, air out my house and try again actually using you measurements. I've gotten too used to just winging it on the amounts of things I use.

Just aim to get the acid down around 3M or 10%. So if you start with 10M / 34% acid, you need to add two parts water (or weak peroxide in our case).

Mixing a strong acid and water like this makes heat. If you toss water into the acid, you'll get hot acid and that might fume. Don't do that.

Measure out two cups of peroxide, pour into that one cup acid. Easy enough, but you need to measure and get the order right.

Open a window anyway, and if you're getting excessive / noticeable fumes rethink what you're doing.

And if you want to ditch a batch of the etchant before use (no copper dissolved in it yet), you can toss some baking soda into it to neutralize the acid and pour it down the drain with a lot of running water.

Elliot the first time I tried this is worked flawlessly. Now I used a small tupperware leftover tub and the boards etched in just a few minutes. I tried it again two nights ago, which was a few weeks later and tried using the still very green solution but I played heck trying to get it to etch. I added a bit more acid but it only seemed to work once I added a little more H2O2. The color didn't change much but the board started losing copper at a more normal rate. Since I bought a laminator and couldn't wait to try it out again last night I threw a couple of small boards in the day old solution and the same result. Just wouldn't etch. Left it in for an hour just to see what would happen and nothing. Added more acid and unfortunately I was out of H2O2. The solution was still nice Kool Aid green too. My wife is picking up some HP today at the store and hopefully when I add that the magic will happen once again. The container is only 4 inches square and maybe 1.5 " deep. You think I should use a larger tub?

Same boat, friend! First batch etches like a dream, but subsequent etches, even if same day, don't complete. Seems a bit of a waste if we have to top off with acid AND H2O2 each time (might as well start from scratch, negating the potential environmental benefits)...

I am having the same issue as you are, my initial solution was PERFECT.

I leave it for a few months, not needing to do any PCBs, come back to it and it is barely etching. I used the "bubble in air" method with no luck, out of HP and will grab some but it seems it is only a temp. workaround and not a solution to the problem.

Were you able to figure out what was wrong? (solution color is LIGHT GREEN)

Help! My attempts only work when I start fresh with HCl and H2O2- when I try to reuse the beautiful emerald green solution, it stalls, and gives me a very bad etch! My solution isn't turning brown, so it has enough oxygen, and it still takes to copper to the rosey stage, so i think it has enough acid. I will try adding more acid, but...

I mixed the acid and peroxide in the correct ratios. I used my vinyl resist and let a piece etch. It wasn't very deep after an hour so I removed the piece. I placed a couple of scrap pieces in the solution for a few hours and they reduced in thickness quite a bit. I then tried etching another piece and it seemed to be slower than the original etch attempt. The solution is still a very light bluish green. Do I need to dissolve more copper in it first?

Indeed it was not a pcb. 16g copper sheeting is what I use in my jewelry making. A piece approximately 1" by 2" with a vinyl resist. It made a decent visible etch initially. I added a I" piece of 1/4" tubIng and about a 1" square piece of scrap to see if that would green it up. Those were quite dissolved after a few hours but after that nothing else would really etch. Thanks. I'll try more acid. Would a 1/1 ratio be better for my needs?

Added a sample of the pieces I'm making. Some of those were done with ferric.

Yeah, you might try a 1/1 ratio for a new starting batch, but at this point you can just top up with a little more acid and see how it goes. The whole point is to avoid re-starting and having to dispose of the copper solution.

Maintaining the chemistry (read: enough free acid & oxygen) is part of the trick with this stuff. When brown, add peroxide. When slow / blue, add acid. Easy enough once you get a feel for it.

My first attempt failed. I used 200ml pool acid (30% HCl) and hydrogen peroxide (400ml 3% H2O2), and after 20 minutes it turned slightly green, and that was it. After 2 hours there is no sign that the copper is coming off of the PCB. I kept it warm and swished it around for the 1st hour, but it looks like nothing is happening to the board; I just left it outside for now - I'll check it in the morning. I need to get more H2O2 to try to tune the batch, but if that doesn't work, I'll have to go back to ferric chloride.

An hour with agitation is waay too long. Especially with fresh chemicals, it should go relatively fast, like ten minutes or so. You can tell it's etching when the shiny and coppery-colored metal goes in -- in a minute or so, it'll turn a matte pink color.

Could anything be coating the copper? Try scrubbing the surface with a bit of sandpaper (finer grit is better for not leaving scratches, but if this is just a test...) beforehand?

I've just finished successfully etching my first board! Someone suggested that the peroxide I bought might be dud: even though I bought it new, if the bottle wasn't properly sealed and it had been on the shelf long enough, he said it could be useless - it had happened to him more than once. So I bought another bottle from a different shop, and hey presto! the board etched in a few minutes. I over did it a little bit, probably because I didn't agitate it evenly: I had to wait for a patch in the middle to dissolve. (Don't swirl: rock!) But it works, so from here it can only get better. I think my main lesson is to keep a few bottles of peroxide handy.

BTW, before my 2nd attempt, I was also wondering if the "gloss" from the glossy paper might have coated the board with an invisible layer of plastic - it seemed possible - but I've now established that that is not the case. The paper works perfectly.

Hey fantastic! I'm glad to hear you got it working, and even more stoked that you found a way that things can go wrong. :)

Peroxide has a shelf life, for sure. And as you note, a trip to the pharmacy and a couple of bucks can test that hypothesis.

Re: agitation is key. The center pretty much always dissolves more slowly than the edges, no matter how you agitate (unless you're spraying, but that's another level of complexity altogether). If you let it sit for a second or two, then swirl, you can see brown/black dust coming off the board -- gives you a good idea of whether you're agitating well enough.

Glad you got it working, and thanks for coming back with the report. Watch out for bad/expired peroxide, y'all!

i use ammonium persulfate. It is in powder form and you mix it with water. It is tranparent so you can see the etch working, it turns slightly blue as etch is working - I use it for etching copper bullet casings, holding the casing with a 'third hand' and putting it into a plastic up with the etching mix. you can see how deeply the etch is going and then pull it out - no fumes, no fuss. I have tried many resists, staz on ink pads with art stamps, black and white prints on photo paper which i then iron onto the casing, hand drawn sharpie pen shapes.... https://www.youtube.com/watch?v=TLf4w1zTpkw

With the cuprous chloride solution, you only have to dispose of the etchant/copper mix once: when you're never going to make any PCBs anymore. Otherwise, you can keep re-using the solution indefinitely. It's just a lot less hassle.

Wow, that's a fantastic result! (And so far away from the boring PCBs I run.)

A resist for longer-term / deeper cutting? Not sure. I've used nail polish sometimes when I need it to hold. Just have to make sure it's fully dry before etching -- a hairdryer can help. But I don't know if you'll get fine enough lines for what you want.

You might look into what engravers use? Sometimes they use some pretty nasty acids, and have a long history of high-resolution resists.

you dont need to dip the whole blade in a pool. Think of a sock and foot/leg. Get a plastic tube container just big enough for it (PVC tube?). you can fill the empty space with a long dowel cut in half. that way its just the blade that is covered in a few MM of liquid.

When you get to the point of too much solution, you could electroplate the dissolved copper onto a piece of copper wire.

Raise the pH of the solution with lye or ammonia (to at least pH 7), stick in a copper cathode and a sacrificial anode, and apply a few volts. You'll want a corrosion-resistant anode, and platinum is rather pricey; perhaps a carbon anode would work?

What ratio did you mix the two. I've a 6% H2O2 and a mix of 9.9% HCL (brick cleaner alright). It's turning green but it isnt etching a thing (only cleaning off the sharpie I used to fix a track on the etching).

Mine was about 3 x HCL to 1 x H2O2 by volume. I've noticed a lot of variation here and people seem to prime it with spare copper to reach optimum speed. These % mixtures are mostly water & seems a lot of people either use air bubbling, agitation or heat to either evaporate off the water or accelerate the reaction. Still experimenting here too!